code: def get_available_backends() -> Dict[str, Type[Backend]]:
      backend_specs: Dict[str, Type[Backend]] = {}
      if lazy_import_ffmpeg_ext().is_available():
          backend_specs["ffmpeg"] = FFmpegBackend
      if lazy_import_sox_ext().is_available():
          backend_specs["sox"] = SoXBackend
      if soundfile_backend._IS_SOUNDFILE_AVAILABLE:
          backend_specs["soundfile"] = SoundfileBackend
      return backend_specs
  
file_path: audio/src/torchaudio/_backend/utils.py
imports: import os
  from functools import lru_cache
  from typing import BinaryIO, Dict, Optional, Tuple, Type, Union
  import torch
  from torchaudio._extension import lazy_import_sox_ext
  from torchaudio.io import CodecConfig
  from torio._extension import lazy_import_ffmpeg_ext
  from .None import soundfile_backend
  from .backend import Backend
  from .common import AudioMetaData
  from .ffmpeg import FFmpegBackend
  from .soundfile import SoundfileBackend
  from .sox import SoXBackend
label_desc: Use image node_id 1 for calling a global function with example usage: get_available_backends() and returns: backend_specs